Women who depend on vitamin supplements to protect their health might want to reconsider. A large study published yesterday in the Archives of Internal Medicine found that most supplements (with the exception of calcium supplements) provide few health benefits, and some may actually do more harm than good.

According to a report in The Wall Street Journal, the study found that some supplements were actually associated with an increased risk of early death. For example, women in the study who took iron supplements were 3.9% more likely to die than those who didn’t. Women who took a multivitamin faced a 2.4% higher risk of early death than those who did not. Other supplements linked to a slightly higher risk of mortality included vitamin B6, folic acid, iron, magnesium, zinc and copper.

The study followed nearly 39,000 women for an average of 19 years, according to the Journal. It assessed supplement use in three questionnaires taken in 1986, 1987 and 2004, and then tracked the death rate in the women. The women in the study were 62-years-old when it started.

Use of supplements rose from 63% of women in 1986 to 85% of women in 2004. During the study more than 15,000 women died, according to The Wall Street Journal. Researchers controlled for factors such as age, diet, weight, smoking status and underlying health conditions to isolate the impact of vitamins and minerals.

The one exception was calcium supplements, which according to MSNBC, appeared to lower the women’s death risk by 3.8 percent. However, there was no link between consuming increasingly higher amounts of calcium and a continuing decrease in mortality rate.

â€œBased on existing evidence, we see little justification for the general and widespread use of dietary supplements,” unless there is a medical reason or deficiency of a particular nutrient, the study authors wrote, according to The Wall Street Journal.

More than half of U.S. adults take vitamins, and consumers spent about $11.8 billion on vitamins and minerals last year, the Journal said.

Lisa Harnack, a professor of epidemiology at the University of Minnesota and a study author, told The Wall Street Journal that “this study, in combination with previous studies, raises safety questions about supplements.”

A 2009 study involving about 161,000 postmenopausal women participating in the federally funded Women’s Health Initiative, for example, found that multivitamin use didn’t cut the risk of cancer, cardiovascular problems or the overall death rate.

Another study author, Jaakko Mursu, an epidemiologist at the University Of Minnesota School Of Public Health, told MyHealthNewsDaily that the increased death risk “could be related to generally high concentration of compounds that these supplements contain. Most supplements contain higher amounts of nutrients than would be derived from food, and it is known that several compounds can be toxic in higher amounts, especially when consumed for a long time, as some of these accumulate to body.”